The mechanism by which a cytoplasmically-synthesised (recombinant) protein is translocated into the periplasmic space of Escherichia coli is known to occur by the workings of the signal hypothesis (see review by Stardler, J. A. and Silhavy, T. J., 1990, Methods in Enzymology, 167-187). Many such proteins are initially synthesised as precursor forms carrying extensions at their amino termini known as signal sequences (peptides). The signal sequence has the information required for selective translocation of the passenger part of the protein molecule across the cytoplasmic membranes of the bacteria. The signal is cleaved off soon after the periplasmically-deposited protein has gained its native biological fold and function.